1. Field of the Invention
The present invention relates to a charge amount measuring method, a shift value measuring method of charged beam, a charge amount measuring device, and a shift value measuring device of charged beam.
2. Description of the Related Art
As supports of charged conductors in electric apparatuses and discharge application apparatuses, solid insulator is widely used. Since interface discharge occurs at interfaces between the solid insulator and surrounding liquid and gas, however, the surface of the solid insulator might be charged. If the solid insulator is charged, the surrounding electric field changes and there is also a risk that the function of an electric apparatus will not be fulfilled. Therefore, it is useful to secure the function of the electric apparatus to measure the charge amount of the solid insulator and measure the influence of the charged solid insulator on surroundings. As conventional methods for measuring charge amounts of insulation materials, the following methods are known. (1) A method of making a sensor approach a surface of an insulation material and measuring a charge amount induced electrostatically in the sensor by surface charge (“Creeping discharge and charge on surface of insulation material,” Journal of The Institute of Electrical Engineers of Japan, Vol. 22, No. 3, 1998). (2) A method of making a Pockels crystal approach a surface of an insulation material and measuring surface charges on the basis of a voltage applied between end faces of the crystal by the Pockels effect (“Study of surface electrometer using Pockels effect,” 2000 National Convention Record, The Institute of Electrical Engineers of Japan 1-064).
In the case of the method of (1), a size being lager than a predetermined size is required as the opposed area of the sensor, and the surface of the insulation material is supposed to be a plane like a sheet. Therefore, the method of (1) has a problem that a probe (resolution) of approximately φ2 mm is minimum in the practical level. Furthermore, the method of (2) also has a problem that a probe of approximately several mm is minimum in the research level for a similar reason and the resolution is kept to approximately half of the probe size. Furthermore, in a technique of forming a measuring surface on the surface of the Pockels crystal, there is a possibility that the resolution of up to a wavelength order will be obtained, but there is a problem that the technique cannot be applied to typical insulation materials because the measuring subject is Pockels crystal itself. In Jpn. Pat. Appln. KOKAI Publication No. 7-288096, there is described a charge detection method of a sample capable of detecting the charged state of the sample automatically and simply. This method is a method of scanning the surface of the sample with an electron beam in a two dimensional manner, detecting a reflected electron signal, and thereby detecting the charge of the sample. However, there is a drawback that the charged state of the sample is changed by scanning the sample with the electron beam and there is a problem as regards the measurement precision.